This invention pertains to catheters and more particularly to an apparatus for placing cardiac pacing leads.
Cardiac pacing leads are used in conjunction with cardiac pacemakers to apply electrical stimuli to the heart causing the heart muscle to contract. This type of stimulation, or pacing, is used in cases where problems occur in the intrinsic electrical system of the heart.
In the past, pacing electrodes were introduced into the right atrium and/or right ventricle of the heart by means of a catheter inserted in the left subclavian vein (or directly via the cephalic vein) through the superior vena cava into the right atrium across the tricuspid valve into the right ventricle. In those cases where it is desirable to apply an electrical pacing pulse to the ventricle only, the pacing electrode is secured to the endocardium or inner lining of the right ventricle. In those cases where coordinated A-V pacing is desired, a second pacing electrode is secured to the inner lining of the right atrium.
In some cases, it is desirable to secure a pacing lead in the coronary sinus whereby an electrical pacing pulse is transmitted to the left ventricle to improve the pumping action of the heart. However, such a procedure has herefore been extremely difficult using traditional catheterization techniques. This is because of several factors including the inconsistency of the location of the Os of the coronary sinus. Also, the heart is in motion, contracting 60 to 100 times a minute. In addition, the course of the coronary sinus beyond the Os may be quite variable. Furthermore, visualization of the course of the coronary sinus and its multiple branches has been suboptimal. Also, passage of the pacing electrode has been hampered by the anatomy of the coronary sinus and its branches as well as a lack of a mechanically stable delivery system that will allow real-time coronary sinus venography during pacing electrode placement.
The present invention comprises an apparatus for placing a pacing electrode in the coronary sinus so as to pace the left ventricle of the heart. This apparatus comprises a preshaped, flexible catheter having a distal end and a predetermined shape in an unflexed or steady state condition to facilitate placement of the distal end into the os of the coronory sinus within the right atrium of the heart. This predetermined shape is imparted to the catheter using a material which, while flexible, imparts a structural memory such that the catheter retains its predetermined shape in its unflexed or steady state condition. The catheter includes a first lumen which extends from an entry port at a proximal end of the catheter through the catheter terminating at an exit port at the distal end of the catheter. The catheter includes a second lumen which extends from a first port in the vicinity of the proximal end of the catheter through the catheter terminating at a second port which is in fluid communication with an inflatable/deflatable balloon in the vicinity of the distal end of the catheter. An inflating/deflating device, such as a syringe, is attachable to the first port of the second lumen, for inflating/deflating the balloon. At least one port, disposed through an outer wall of the catheter on a distal side of the balloon, is in fluid communication with at least one port disposed through the outer wall of the catheter on a proximal side of the balloon. The apparatus also includes a pacing lead with over-the-wire capability which is removably insertable through the first lumen of the catheter.